The present invention relates to an electrostatic copier, and more especially to an electrostatic copier of the type having a device for removing residual toner particles from the photoconductive surface of a travelling endless image-pattern carrier.
Electrostatic copiers are known per se and their construction and basic operation need not be described. It will suffice to point out that after an image has been formed on the electrostatically charged photoconductive surface of the carrier and this image has thereafter been transferred to the image carrier, some residual toner particles will continue to adhere to the photoconductive surface. These particles must be removed before the next image-pattern is formed on the photoconductive surface, because their presence would lead to smeared or otherwise unsatisfactory images during succeeding operations of the copier.
It has been proposed to remove these residual toner particles from the photoconductive surface by a cleaning roller which mechanically brushes the surface and picks up the particles from the same. These particles are then transferred from the roller to a strip-shaped fibrous web that is incrementally withdrawn from a supply roller and taken up on a take-up roller. Such an arrangement would have the advantage of successively presenting clean portions of the incrementally advanced web to the cleaning roller from which they pick up the toner particles. However, such operation results, of course, in exhaustion of the web supply on the supply roller and necessitates a relatively frequent replacement of the empty supply roller with a refilled new supply roller. This not only leads to the need to constantly replace the web as a consumable commodity, but also requires that the cleaning device be withdrawn from the copier housing, the used web be removed, a fresh supply roller be installed and the leading end of the fresh web be connected to the take-up roll before the device can be re-inserted into the copier housing. All of this is relatively complicated and most certainly time-consuming. Therefore, this proposal does not represent the optimum desired solution which should make operation as simple as possible for the user and should, ideally, remove or reduce to a minimum the use of consumable commodities in connection with the cleaning operation.
Another previous proposal seeks to remove residual toner particles from the cleaning roller by means of a doctor blade. This, however, is quite unsatisfactory because some of the particles removed from the cleaning roller inevitably adhere to the doctor blade. Since this effect is cumulative, the doctor blade becomes so encrusted with adhereing particles over a period of time, that in relatively short order the cleaning effectiveness has dropped to a totally unsatisfactory level.